This invention relates to a pneumatic distribution system of the type comprising a tank for containing a particulate material to be distributed, a plurality of distribution ducts, metering means for feeding the material from the tank into each of the ducts at a measured rate, an airflow system for transporting the material along the ducts, and means mounting the ducts such that the ducts extend outwardly from the tank to respective sides of the tank for spreading of the material across the ground as the tank is moved forwardly on a suitable transport mechanism.
Pneumatic distribution devices of this type are well known and are used agriculturally for distribution of seeds, fertilizer and other granular materials. One example of a device of this type is shown in U.S. Pat. No. 4,569,486 (Balmer) in which each duct includes a rigid straight tubular pipe extending outwardly from an inner end adjacent a tank to outer end of the pipe which constitutes the end of the duct. A spreader nozzle is mounted on the end of the pipe for directly receiving the material moving longitudinally of the pipe and for redirecting that material into a spread pattern which generally requires the material to be turned either forwardly or rearwardly from the pipe and then downwardly toward the ground in the spread pattern.
As the purpose of the device is to spread the material evenly across the ground, it is generally necessary to have the spreader nozzles arranged relatively closely at a spacing of the order of two to four feet. In order to produce a distribution device which has a operating width of up to 60 feet it will be appreciated that a large number of spreader nozzles is required. As each spreader nozzle thus is connected to a separate duct and each duct requires the necessary metering and air blower arrangements, it will be appreciated that increases in width of the distribution device carry a heavy financial penalty for the costs of the equipment required.
It has been appreciated that savings in cost can be achieved by providing a reduced number of ducts and then splitting the material from each duct into spreader nozzles which act at a different point across the width of the device. Thus U.S. Pat. No. 4,073,439 (Grataloup-corresponding to Canadian Pat. No. 1,039,326) discloses an arrangement in which at the end of the distribution pipe a nozzle is provided which has a first nozzle part close to the end of the pipe and a second nozzle part spaced outwardly from the end of the pipe so as to form two nozzle parts spaced across the width of the machine each supplied from the same distribution pipe. The single distribution pipe of course has to be of larger diameter to accommodate the increase in material but the increase in diameter certainly does not double the cost of the pipe and in addition only a single metering part is necessary for the single pipe and a reduced amount of air movement is necessary to transport the material through the pipe of increased diameter.
However, the nozzle device of Grataloup has not been entirely satisfactory and has not achieved significant success in the field. In particular the construction of the nozzle itself is of a complex nature and accordingly is an expensive item relative to the cost of two individual nozzles.